polyethene
addition polymer
plastic bottles, toys, plastic bags, film wrap
polychloroethene/PVC
addition polymer
plastic pipes, artificial leather, wire insulation
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polyethene
addition polymer
plastic bottles, toys, plastic bags, film wrap
polychloroethene/PVC
addition polymer
plastic pipes, artificial leather, wire insulation
PTFE
addition polymer
coating for non-stick pans
polypropene
addition polymer
lab equipment, automobile parts
polystyrene
addition polymer
styrofoam
starch/glucose
enzymes act as biological catalysts
condensation polymerisation of glucose (monomer) into starch (polyamide) + water
reverse: hydrolysis, break down polymer into monomers using water
polyethylene terephthalate (PET)
low permeability to CO2, used in bottling of canned drinks
kevlar
polyamide with benzene ring
spider silk (naturally occuring)
polypeptide
polyamide formed from amino acids
renewable energy sources
naturally replenished, will not run out
biofuels
solar energy
wind
hydroelectric
tidal
geothermal
nuclear fusion
non-renewable energy sources
finite, will run out
fossil fuels (coal oil natural gas)
nuclear fission
electrochemical cells: redox reaction generates electricity
formation of fossil fuels
plant matter contains CHO from photosynthesis (glucose) + contains N and S because of protein. plants consumed by animals.
anaerobic decay of biological material: absence of oxygen, compressed and acted on by bacteria
coal
formed from remains of plants that were buried → partial decomposition in absence of oxygen, high temperature and pressure
mostly carbon, also HONS
% of C increases, burn more cleanly and releases more heat on combustion
advantages
supply should last 100s of years
distributed throughout the world
can be converted to synthetic gaseous/liquid fuels
can be converted to feedstock for the petrochemical industry
more concentrated source of energy
relatively cheap to produce
disadvantages
produces greenhouse gases when burned → climate change
acid rain + particulates
less easy to transport
mining is dirty and dangerous
crude oil (petroleum)
formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)
is a mixture of hydrocarbons, also ONS
advantages
easier to extract and transport than coal
convenient for internal combustion engine
source of variety of chemicals for the petrochemical industry
disadvantages
produces greenhouse gases when burned → climate change
acid rain
supply could run out in decades
extraction + transportation in tankers → env issues
few countries have reserves
natural gas
formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)
mostly CH4 and light hydrocarbons and HS
advantages
cleanest fossil fuel due to low % of C
easiest to extract and transport (using pipes)
releases highest amount of energy per mass of fuel
produces least CO2 per J of energy
cheap to produce: is a byproduct of coal/oil production
disadvantages
produces greenhouse gases when burned → climate change
acid rain
supply could last less than 100 years
few countries have reserves
risk of explosions due to leaks
most difficult to store because it is a gas: need store under pressure or cool to liquefy it
ways of comparing fossil fuels
CO2 produced per J
vol or mol of CO2 / energy divided by 1000 = __ mol CO2 J -1
lowest = greenest (natural gas)
vol of fuel per mass of fuel
no. of mol x 22.7 divided by mass = __dm3g-1
only if at STP
mass of CO2 produced per gram of fuel burned
mol x 44.01 = mass of CO2
mass of CO2/Mr of fuel = __g
carbon footprint
mass of fuel consumed = density x volume
no. of mol of fuel consumed = mass/Mr
mol ratio to find no. of mol of CO2 produced
mass of CO2 = no. of mol x 44.01 = __g
how could samples be distinguished by combustion?
calculate % of C for each sample. sample with higher % of C has higher tendency for incomplete combustion, will produce more soot when burnt.
greenhouse effect
initial: some IR reflected back into space, some reach earth’s surface, some absorbed by greenhouse gases then re-radiated back to earth
earth’s surface emits IR radiation, absorbed by molecules of greenhouse gases (CO2, CH4, NOx) → promote to higher energy levels, vibrate more → as move down to ground state, energy given out in all directions → some IR radiation radiated back to earth
recall IR spec: only for asymmetric stretch and symmetric bend since there is change in dipole moment
carbon dioxide has greater influence on global warming: even though doesn’t absorb much IR radiation, produced in greater amounts
net effect: higher % of solar energy is trapped in atmosphere → higher average global temperatures
impact: crop yields decrease, biodistribution (due to desertification and loss of cold-water habitats), rising sea levels (due to melting of ice caps)
biofuels
plants have CHO because of photosynthesis producing glucose → plant material transformed into fuel
advantages
renewable source of energy
can be produced locally, no need expensive oil imports
can be produced from waste materials
ethanol as biofuel
formed from fermentation of glucose
C6H12O6 (aq) → 2C5H5OH (aq) + 2CO2 (g)
conditions: ethanol, yeast catalyst, 37C, absence of oxygen (prevent oxidation of ethanol)
produces mixture of water, aldehydes, other alcohols and around 8% ethanol, need distillation to concentrate % of ethanol
methanol poisoning
max concentration 15% ethanol since higher concentration will poison the yeast
exothermic reaction, need control temperature otherwise will denature enzymes and kill yeast
advantages
lower greenhouse emissions: produces CO2 but the C in ethanol came from atmosphere (absorbed by plants), so theoretically ‘carbon neutral’
renewable, produced locally
disadvantages
lower specific energy than gasoline, need larger volume for same amount of energy
absorbs moisture from atm, damages engine
production of ethanol is energy intensive (distillation)
food vs fuel, price of food increases
biodiesel
formed from transesterification of vegetable oils
3 fatty acids (carboxylic acid) + glycerol (triol) → vegetable oils (triglyceride, 3 ester linkages)
methanol react with vegetable oil → fatty acid ester link to methanol
condition: strong base catalyst
reversible reaction, so excess methanol added to shift POE to right
advantages
biodegradable, less env impact from spillage
no S, no SO2
better lubricant than petrodiesel (reduce engine wear)
theoretically carbon neutral
disadvantages
higher NOx emissions
more expensive than petrodiesel
lower specific energy than petrodiesel, need larger volume for same amount of energy
production is energy intensive
food vs fuel, price of food increases
loss of biodiversity for palm oil plantations